Abstract
The charged particle central rapidity density per participant nucleon pair ((dN(ch)/d eta)/(0.5 < Npart >)) as a function of the average number of participants (N-part) for Au + Au (Cu + Cu) collisions at root s(NN) = 62.4 and 200 GeV, and Pb + Pb collisions at root s(NN) = 2.76 and 5.02 TeV is investigated within an improved HIJING (ImHIJING/Cas) model. Compared to the standard HIJING version, it incorporates: i) more consistent parton densities, ii) a QCD running coupling, defined by the exact solution of the renormalization group equation, and iii) a spatial dependent nucleon shadowing, triggered by collective nucleon interactions with an incoming nucleon, and simulated by the collective cascade recipe. Predictions are compared using four different settings of nuclear shadowing of partons, based on the standard HIJING1.0(2.0) parameterizations. It is shown that ImHIJING/Cas/Set2 (that with both quark and soft gluon shadowing of strength s(q(g))) can nicely reproduce the measured centrality dependence of (dN(ch)/d eta)/(0.5 < N-part >) at RHIC energy. As for LHC, a reduction of s(g) by similar to 40% at very peripheral (90-100%) Pb + Pb collisions, as compared to free nucleon-nucleon collisions, is found to reproduce the measured data. The values of s(q(g)) used in ImHIJING/Cas/Set2 calculations for most central 0-3(5)% Au + Au(Pb + Pb) collisions at RHIC(LHC) energy, are found to be consistent with those employed in Set2 that reproduce the measured structure function ratios (12F(2)(Pb)/207F(2)(C)) as a function of x.